Department of Physics, Ben-Gurion University of the Negev, P. 0. Box 653, Be'er Sheva 84105, Israel;
Ioffe Physical-Technical Institute, Polytechnicheskaya 26, St. Petersburg 194021, Russia;
Department of Chemical Science and Technology, Hosei University, 3-7-2, Kajino, Koganei, Tokyo 184-8584, Japan;